Define EMF models via annotated interfaces

2.1. Overview

EMF allows to use annotated Java interfaces to define the data model. The annotations used are Javadoc annotations. Each attribute or class that is a part of the EMF model must have a @model tag and may have an optional list of additional attributes.

The @model tag may be followed by additional details about the model element. For example, if an attribute should be read-only (no generation of a set method),the following annotation needs to be added: changeable="false".

2.2. Annotations Tags

The following tags can be used in the @model definition:

Table 1. Java Annotations

Annotation	Description
abstract="true"	Creates a abstract class
containment="true"	Express UML2 composition relationships (links with black diamonds). These objects references are saved with the object.
default=Value	Default value, can be a constant, enumeration.
changeable="false"	No setter will be generated

Tip

If a list is flagged with Containment="true" then elements of a list A are automatically removed from list A if the added to another list B. This is very powerful but important to know.

2.3. Data Model

We will model a webpage structure with EMF.

Create a new Java project called "sawan.modi.emf.webpage". Create a new folder called "metamodel" which will contain the EMF model.

Create the following interfaces.

    
package sawan.modi.emf.webpage.model;
/**
* @model
*/
public interface Article {
 /**
  * @model default=""
  */
 public String getName();

}

   

    
package sawan.modi.emf.webpage.model;

import java.util.List;

/**
* @model
*/
public interface Category {
 /**
  * @model default=""
  */
 public String getName();

 /**
  * @model containment="true"
  */
 public List
 getArticles();
}

   

    
package sawan.modi.emf.webpage.model;
import java.util.List;

/**
* @model
*/
public interface Webpage {
 /**
  * @model default=""
  */
 public String getName();

 /**
  * @model default=""
  */
 public String getTitle();

 /**
  * @model default=""
  */
 public String getDescription();

 /**
  * @model default=""
  */
 public String getKeywords();

 /**
  * @model containment="true"
  */
 public List getCategories();
}


   

    
package sawan.modi.emf.webpage.model;

import java.util.List;

/**
* @model
*/
public interface MyWeb {
 /**
  * @model default=""
  */
 public String getName();
 /**
  * @model default=""
  */
 public String getTitle();
 /**
  * @model default=""
  */
 public String getDescription();

 /**
  * @model default=""
  */
 public String getKeywords();
 /**
  * @model containment="true"
  */
 public List getPages();
}

 
   

2.4. Create EMF Meta Model

Create a new EMF meta model "website.genmodel" based on these interfaces in folder "metamodel".

Select your metamodel folder, right click and select Other. Select Eclipse Modeling Framework -> EMF Generator Model

Press next and select the following.

Press next and you should be able to select your package. Change the name of the ecore model to "website.ecore".

Press finish. You have created your EMF model! We will discuss this model in the next chapter.

To use your model in an plugin environment later. Add the util package to your exported packages in MANIFEST.MF on tab Runtime.